1. Field of the Invention
The present invention relates to a hybrid vehicle, and particularly, to a hybrid vehicle equipped with a four-stroke cycle linear engine that provides capacity for charging a high-capacity battery, using a HCCI (Homogeneous Charge Compression Ignition), and a method of operating the engine.
2. Description of Related Art
Hybrid vehicles that are manufactured for external environmental factors, such as eco-friendship and high oil price necessarily have low output relatively to gasoline engines or diesel engines because the thermal efficiency of hydrogen fuel is low, but the low output of the engine can be compensated by a power distribution ratio similar to a motor or power distribution ratio biased to the motor due to the characteristics using the engine and the motor together.
Further, when a hybrid vehicle is equipped with a large-capacity battery, a high-output motor can be used and the performance of the vehicle can be greatly increased and the possibility of using apparatuses with various performances using electric power is largely increased, such that common use of the hybrid vehicle is made considerably earlier and the commercial quality can also be improved.
In general, since a large-capacity battery need to be continually charged so it needs a high-output power generator and the high-output power generator necessarily needs a high-output engine.
Therefore, a high-output engine must be mounted first in order to apply a large-capacity battery on a hybrid vehicle.
In general, it is possible to increase output by increasing the thermal efficiency of fuel, which is implemented by only ignition method without changing the engine structure, for example, HCCI (Homogeneous Charge Compression Ignition).
However, the HCCI combustion control is suitable for a diesel engine generating high pressure or a gasoline engine with lower compression pressure relatively to the diesel engine, but it generates a relative large power loss ratio to apply the HCCI combustion control to the engine of a hybrid vehicle, such that there is technical difficulty in practical use in terms of efficiency.
It is possible to somewhat minimize the power loss ratio of the engine described above by employing a two-stroke cycle type linear engine instead of a four-stroke cycle gasoline engine or a diesel engine in a hybrid vehicle.
However, the two-stroke cycle type linear engine has a limit in increasing the compression ratio for the characteristics in comparison with the gasoline engine or the diesel engine and the limit in increasing the compression ratio makes the HCCI combustion control impossible, such that HCCI combustion control is difficult to be applied in a hybrid vehicle.
That is, in a hybrid vehicle equipped with a two-stroke cycle type linear engine, the output of the power generator is necessarily low because the output of the engine is low, and a low-capacity battery is used, corresponding to the low-output power generator, such that it is difficult to overcome the limit in the related art, the decrease in performance and commercial quality of the hybrid vehicle.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.